Pancreatic ductal adenocarcinoma (PDA) is among the most lethal of all human malignancies. A key clinical challenge is the propensity of these tumors for early invasion and metastasis. Thus, most patients are not eligible for resection, and those who are often show recurrent disease. This challenge is compounded by the absence of methods for early detection of invasive disease and incomplete understanding of the mechanisms for PDA progression. Our discovery of the fetal RNA-binding protein Lin28b as a major driver in PDA metastasis provides a framework to address these critical issues in this multiple-PI proposal. In previous studies, we have found that the oncofetal RNA-binding protein Lin28b is highly upregulated in PDA, both in murine models and human patient samples. Furthermore, new preliminary data indicate that Lin28b is specifically upregulated in Circulating Tumor Cells (CTCs) obtained from patients with early resectable PDA. Based on these findings, we hypothesize that Lin28b drives PDA progression and metastasis by reprogramming cell differentiation toward a more primitive progenitor-like state, and that detection of Lin28b in CTCs can serve as a molecular beacon for disease aggressiveness.In order to test this hypothesis, we will: 1- Characterize Lin28b as a driver of self renewal and tumor progression in human and murine PDA models. We will take advantage of ex-vivo grown organoids from human CTCs and specific genetically engineered mouse models of PDA to genetically manipulate Lin28b and determine tumor propagating cell function and ability to drive PDA progression. 2- Determine the mechanisms through which Lin28b could drive agressiveness, exploring its downstream targets (linked to the microRNA let-7), and the biological and metabolic features driven by this oncofetal protein. 3- Evaluate Lin28b as a predictive biomarker of PDA early disease recurrence, taking advantage of CTCs isolated from human patients undergoing surgical resection.